1. Field of the Invention
The invention relates to a power output apparatus, a method of controlling the power output apparatus, and a vehicle on which the power output apparatus is installed.
2. Description of the Related Art
A conventional power output apparatus installed on a vehicle includes an engine, a planetary gear mechanism connected to a crankshaft of the engine and also connected to a rotary shaft, a first motor (MG1) connected to the planetary gear mechanism, a second motor (MG2) connected to the rotary shaft, and a transmission that transmits power from the rotary shaft to driving wheels while changing the rotational speed (as described in, for example, Japanese Patent Application Publication No. 2007-261562 (JP-A-2007-261562)). In the power output apparatus, when the engine is started while the rotary shaft is disconnected from the driving wheels via the transmission, the motor is controlled so that a given current passes through the d axis at a start-time electric angle as an electric angle used when fixing the direction of a magnetic field formed by a stator of the motor MG2. As a result, torque (torque of attraction) corresponding to a difference between the start-time electric angle and the current electric angle is applied to the rotary shaft, and the rotor is stopped at a position where the torque of attraction and torque (applied torque) generated from the motor MG1 and applied to the motor MG1 are balanced with each other, so that the engine can be started by motoring even in a condition where the rotary shaft is disconnected from the driving wheels.
In the power output apparatus as described above, when the given current is passed through the d axis at the start-time electric angle, the rotor may rotate if the applied torque is larger than the maximum torque (the maximum value of the torque of attraction) that can restrict or inhibit rotation of the rotor with the given current. In this case, too, it is desirable to curb or prevent rotation of the rotor to the extent possible.